The Achiga Girls' Academy in Nara once defeated regional mahjong powerhouse Bansei High School. It advanced into the national team semifinals but lost to the eventual champion, and the mahjong club was later disbanded.

Six years later, elementary school student Shizuno Takakamo befriends transfer student Nodoka Haramura. The two eventually enter Achiga Girls', but Nodoka transfers out of the school in the second year.

When Shizuno sees Nodoka on television the following year as the national middle school individual mahjong champion, she decides to revive Achiga's mahjong club.

Saki Miyanaga, along with the rest of Kiyosumi High School's mahjong team, proceeds to the national level of the Interhigh Mahjong Championship. However, reaching the top will prove difficult as she faces opponents on par with and, quite possibly, exceeding her skills. Even so, she refuses to back down, vowing to stop at nothing to fulfill her goal: to see her sister face-to-face once more. [Written by MAL Rewrite]

Kouta Hasegawa is a completely normal high school student who likes his Pompompurin stuffed animal, a Sanrio character modelled after a Golden Retriever, which his grandmother gave him when he was young. However, an incident in which other kids accused him of being girly for liking Sanrio characters made him ashamed of his attachment to Pompompurin. Through a series of unexpected events, Kouta ends up meeting others at school who also like Sanrio characters—Yuu Mizuno, a flashy boy who is popular with girls; Shunsuke Yoshino, a member of the soccer team; Ryou Nishimiya, an underclassman who is a library assistant; and Seiichirou Minamoto, the student council president. Through his new friends, Kouta learns that there is no need to be embarrassed for liking Sanrio characters; and together, they aim to create a play for the cultural festival in order to transform his normal school life into a sparkly one. [Written by MAL Rewrite]

After losing both parents in a fatal plane crash, teenager Ryuuichi Kashima must adjust to his new life as the guardian of his younger brother Kotarou. Although Ryuuichi is able to maintain a friendly and kindhearted demeanor, Kotarou is a reserved toddler still too young to understand the reality of the situation. At their parents' funeral, they are approached by Youko Morinomiya, the stern chairman of an elite academy, who decides to take them under her care. However, there is one condition Ryuuichi must fulfill in exchange for a roof over their heads and enrolment in the school—he must become the school's babysitter. In an effort to support the female teachers at the academy, a babysitter's club was established to look after their infant children; unfortunately, the club is severely short-staffed, so now not only is Ryuuichi responsible for his little brother, but also a handful of toddlers who possess dynamic personalities. [Written by MAL Rewrite]